*{
    padding: 0;
    margin: 0;
}
a{
    text-decoration: none;
}
header{
    height: 50px;
    line-height: 48px;
    background-color: #20232a;
}
nav{
    width: 1200px;
    margin: 0 auto;
}
header a{
    display: inline-block;
    height: 48px;
    padding: 0 15px;
    color: #fff;
}
header .active{
    border-bottom: 2px solid rgb(97, 218, 251);
    color: rgb(97, 218, 251);
}